[FIX] base: validate disable_counters

An attribute 'disable_counters' on fields of the search panel is
supported in case performance issues would be encountered with counters.
The commit dd7022ec
allowing to use the search panel in other views than the kanban views
has also introduced the search panel arch validation
and the attribute 'disable_counters' was forgotten, so that it was
impossible to use it in practice.
With the present commit, 'disable_counters' is now recognized
as a valide attribute.

closes odoo/odoo#50525

Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>

odoo/addons/base/rng/common.rng

@@ -234,6 +234,7 @@
             <rng:optional><rng:attribute name="group"/></rng:optional>
             <rng:optional><rng:attribute name="color"/></rng:optional>
             <rng:optional><rng:attribute name="groupby"/></rng:optional>
+            <rng:optional><rng:attribute name="disable_counters"/></rng:optional>
             <rng:optional><rng:attribute name="operator"/></rng:optional>
             <rng:optional><rng:attribute name="colspan"/></rng:optional>
             <rng:optional><rng:attribute name="nolabel"/></rng:optional>